<!doctype html>
<html>

<head>
    <meta charset="utf-8">

</head>

<h2>汽车品牌选择</h2>
<select name="car_list" id="car_list" onchange=my_func()>
    <option value="changan">长安</option>
    <option value="byd">比亚迪</option>
    <option value="changcheng">长城</option>
    <option value="qirui">奇瑞</option>
</select>
<p>你选择的汽车品牌是:<span id="dd"></span></p>

<script>
    function my_func() {
        var car = document.getElementById('car_list').value;
        document.getElementById("dd").innerHTML=car;
    }
</script>

</html>